The data communication demands of mobile devices are increasing, particularly with the development of rich multimedia applications which run on such devices. Although a mobile device may have sporadic access to high-speed WiFi connections, often when the device is not particularly mobile (e.g. when in the home, workplace or a hotspot), the rest of the time the data transfer rates to the device are limited by the cellular network (e.g. the 3G network) or other wireless access network infrastructure. Data transfer over this infrastructure is often capped by the subscription data plans offered by a service provider and multimedia applications can easily reach the limited monthly caps. In addition (or instead) the charging structure applied by a service provider can mean that high data usage is very expensive. These mechanisms (caps and/or charging schedules) which artificially constrain data transfer demands may be used by service providers because the backhaul capacity of their network would otherwise be insufficient to meet user demands.
A technique which has been proposed to increase capacity is to use devices in the network, which may be user devices or dedicated devices, to act as relays for data. A relay receives data from one nearby device and transmits the data to another nearby device.
The embodiments described below are not limited to implementations which solve any or all of the disadvantages of known relaying methods and systems.